Mercury switch



April 24, 1951 A. c. LINDSII'RCM 2,550,073

MERCURY SWITCH Filed Sept. 29, 1947 1/ l3 23 :2/ 5x 7 26 Q l5 f 1- 6 AV/Wm? QW: M a.

Patented Apr. 24, 1951 MERCURY SWITCH Alrik Giver Linds'triim, Stockholm, Sweden 7 Application September 29, 1947, Serial No. 776,645

In Sweden January 24, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires January 24, 1966 Claims.

This invention relates to improvements in mercury switches in which the current interrupting takes place in a closed receptacle either between two mercury masses or between a mercury mass and one or moresolid metallic electrodes; and the object of the improvement is to prevent the mercury mass or masses and/or the solid metallic electrodes in the receptacle from being oxidized.

Hitherto, receptacles of mercury switches of the type described are usually filled with an inert or reducing gas preventing the mercury mass 01' the solid electrodes from being oxidized as an oxidation would immediately cause a breakdown of service. -The best results are obviously obtained with a filling of reducing gas such as hydrogen. However, using of hydrogen has the drawback that it is very difficult to effectively enclose this gas which after a shorter or longer time diffuses through all materials usable for receptacles of the kind described. The place of the diffused hydrogen is instead taken by air which enters from the surrounding atmosphere or is emitted from portions of the receptacle. This may result in that the hydrogen left is unable to reduce oxygen, present in the air with the result that, for instance, the mercury mass is oxidized and the switch is made useless.

Instead of depending upon a filling of a gaseous substance for the reducing action I employ a solid or semisolid material emitting a gas or a vapor of inert or reducing nature. hf it may be impossible to avoid certain air quantities, however small, entering the receptacle it will be necessary to choose a material emitting a reducing gas or vapor so that the latter is capable of combining with the oxygen present in said air quantities with the result that said oxygen is rendered harmless.

In order to prevent the material emitting the inert or reducing gas or vapor from affecting the mercury mass or other electrodes in the receptacle in some way or other said material is placed into a separate section, e. g. a bore or a cavity, in the receptacle so that it never can come in contact with the mercury mass or the solid electrodes. Said separate section must be placed in such a manner that it does not lie in the path of the arcs so that the material is not subjected to the influence of the arcs.

The emitted gas or vapor must be relatively permanent as well as its products of oxidation. It must not be decomposed into products which may have a prejudicial influence upon the mercury mass or upon solid metallic electrodes. For instance, it should not produce free carbon which may settle as alayer over the mercury mass and the solid electrodes.

As examples of suitable materials emitting a reducing gas, there may be mentioned substances as resins, synthetic resins, lacquers or the like dissolving in relatively easily volatile reducing substances, e. g. alcohols, aldehydes or ketones so that the former substances may accumulate a certain quantity of said reducing substances which are then gradually emitted.

Good results are obtained in using polyvinyl acetate partly dissolved in ethyl alcohol so that the material has a semisolid consistency.

The vapors of alcohols, aldehydes or ketones difier from hydrogen in consisting of substantially larger molecules with the result that they do not diiiuse through various materials in the same extent as hydrogen.

As it is of importance that the material attached to the inside of the receptacle is capable of emitting the desired gas or vapor during a long time, it may not change in such way in course of time that the gas or vapor ceases. Thus, for instance, one should not use resins or synthetic resins hardening in course of time so that the dissolving agent producing the gas or vapor can no longer escape therefrom. Instead of resins or the like also porous substances may be used, which, for instance, suck up a volatile liquid that then emits a reducing vapor. Both the inert gas or vapor and the agent used for accumulating it may also consist of mixtures of various substances. I

A receptacle of a mercury switch provided with a material of the kind described need not to be evacuated or filled with an inert or, reducing gas, such as hydrogen. It will be seen that this substantially simplifies the manuface ture of mercury switches so that the price of the latter is reduced. On the other hand, a first filling with hydrogen may sometimes be favourable as it obviously expels the air out of the receptacle in an effective way.

Such a quantity of the material described must be used that it is capable of reducing both the quantity oxygen present in the receptacle when the switch is manufactured and the quantity switch.

A preferred embodiment of the switch according to the invention will be described hereinafter with reference to the accompanying drawing, in which Figs. 1 and 2 are two sectional elevations at right angles to each other.

In the drawing, l designates a base plate and 2, 3 two resilient arms attached thereto. The mercury switch proper is rotatably supported by these arms which by their outer ends embrace pivots 6 and I on the switch. The arms 2 and 3 also serve as electrical connections between the rotary switch and the Wires 4 and 5 constituting part of the circuit which is to be opened and closed by the switch. The switch is operated by a lever 8 projecting through a slot 9 in a cover l enclosing the switch.

The switch consists of a receptacle composed of a short tubular part i l of electrically insulating material such as ceramic material, artificial resin or the like, the ends of said tubular part being closed by plates 12 and I3 of any suitable metal, for instance iron or steel. The abovementioned pivots 6 and l are integral with small washers I and I6 which are soldered to the plates [2 and I3. Preferably the pivots and washers are made of a highly conductive metal, as for instance brass, with a view to ensuring a good electrical contact with the arms 2 and 3.

The receptacle thus formed is partly filled with mercury mass 20 adapted to form metallic contact between the two electrodes of the switch, namely the plates l2 and I3. Provided centrally of the receptacle is a wall 2| of insulating material, preferably made integral with the tubular part I l and having an aperture 22 located eccentrically in relation to the axis of rotation of the switch so as to be wholly above the mercury level in the one end position of the switch (shown in dotted lines in Fig. 2) and immersed in the mercury, when the switch is rocked to its opposite end position. Thus, in the one end position the mercury mass is divided by the wall 2| into two separate halves and the electrical connection is broken, whereas in the other end position of the switch the aperture 22 is filled with mercury, so that the whole of the mercury mass constitutes a coherent unit and forms a metallic connection between the electrodes I2 and 13.

In the centre of the wall 2| there is provided on each side a shoulder 23 and 24 respectively which prevent the electric are from reaching the solid metal electrodes 12 and 13. A cavity 25 is provided in the shoulder 23 and the wall 21 and isifllled with a material 26 emitting a gas of inert or, preferably, reducing nature. Said material has such solid or semisolid consistency that it cannot escape from the cavity 25. The material 26, due to its location in the cavity 25 is prevented from being struck by the electric are produced when an electric current is interrupted by means of the switch. If the material 26 is a material emitting a reducing vapour, e. g. a synthetic resin dissolved in ethyl alcohol, the receptacle need not be evacuated or filled with an inert or reducing gas, the costs of manufacturing the switch being thus substantially reduced.

The embodiment described and shown in the drawing is to be considered only as an illustration of the principle of the invention and is not restrictive of its scope, as modifications in several respects are possible without departing from the inventive idea as set ,forth in the appended claims. For instance, the invention may also be used in conventional mercury switches having a glass receptacle and two or more electrodes projecting into the receptacle.

What I claim is:

1. In a mercury switch, a closed receptacle, at least one mercury mass in said receptacle, a cavity in said receptacle separated from the space taken up by the mercury mass and separated from the path followed by a normal arc occurring in said receptacle when a current interruption takes place, a material in said cavity emitting a reducing vapor, which material has at least such a semi-solid consistency that said material remains in said cavity.

2. In a mercury switch, a closed receptacle, a mercury mass in said receptacle adapted to complete and interrupt an electrical connection, a cavity in said receptacle separated from the space taken up by the mercury mass, said cavity also being separated from the path followed by a normal are occurring in said receptacle when interruption of an electrical connection takes place, and a semi-solid material within said cavity adapted to emit a reducing gas whereby oxidation within said receptacle is prevented, said gasemitting material having a consistency suflicient to remain within said cavity during operation of the switch and comprising a solid substance partially dissolved in a relatively easily volatilized solvent of a reducing nature.

3. A mercury switch as claimed in claim 2 wherein said material consists of a synthetic resin which is at least partly dissolved in an alcohol of a reducing nature.

4. A mercury switch as claimed in claim 2 wherein said material consists of a quantity of polyvinyl acetate which is at least partly dissolved in ethyl alcohol.

5. In a mercury switch, a closed receptacle, a mercury mass in said receptacle adapted to complete and interrupt an electrical connection, a cavity in said receptacle separated from the space taken up by the mercury mass, said cavity also being separated from the path followed by a normal are occurring in said receptacle when interruption of an electrical connection takes place, and a semi-solid material within said cavity adapted to emit a reducing gas whereby oxidation within said receptacle is prevented, said gasemitting, semi-solid material comprising a mixture of a solid substance and a relatively easily volatilized reducing liquid, having a consistency sufficient to remain within said cavity during operation of the switch.

ALRIK CIVER LINos'rRoM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,256,380 Schmidt Feb. 12, 1918 1,536,439 Knutsson May 5, 1925 1,905,813 Davis Apr. 25, 1933 2,132,920 Bear Oct. 11, 1938 2,155,276 Korndorfer Apr. 18, 1939 2,207,710 Bear July 16, 1940 FOREIGN PATENTS Number Country Date 312,002 Germany May 9, 1919 

